Evidence of East-West Structure in Large-Scale F-Region Plasma Enhancements in the Auroral Zone.

摘要

Large-scale (10- to 100-km) plasma-density enhancements appear to be an integral feature of the auroral F-layer ionosphere. These enhancements, called F-region blobs, have been detected with the Chatanika incoherent-scatter radar, and are particularly noticeable during recent years of high solar activity. Blobs have attracted considerable interest because of their propensity for structuring, apparently via the gradient-drift and current-convective instabilities. Although both mechanisms predict the generation of longitudinal structure, no measurements have been made to verify this hypothesis. In this report, we present the first direct evidence that blobs have east-west structure. The observed longitudinal structure is shown to be consistent with the production of a blob by locally intense particle precipitation at the largest scales (approx. 500 km) and the structuring of the blob by the gradient-drift instability at intermediate scales (similar to 150 km). (Author)